How to determinw hich abs/ trac control sensor

One of my ABS or Traction Control sensors is bad because both pf the lights are on. I need to know how to determine which one is the bad one so i can replace it.
Thanks,
Soctt

I've always been told that it was required to use a tech-scan with ABS module in order to read the various error codes and determine which sensor is defective. If there is a way to check via a vom meter at each sensor - I am unaware of the procedure - but would love to know.

I just had the dealership scan my car for $58.00 to determine which sensor was bad and I am now in the process of changing it myself. Dealer cost parts and labor = $511 / my price for parts = $164 (left rear sensor).